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How to run MD array with help assembly command (pos. degraded) from Linux shell

without comments

Assuming you have added the DEVICE and ARRAY entries to the /etc/mdadm.conf.
Starting the array can be accomplished with a single command:

root@localhost / # mdadm --assemble --scan
 mdadm: /dev/md0 has been started with 6 drives.
root@localhost / #

For those who have not added the array configuration information to the /etc/mdadm.conf file there is still hope yet. Starting the array without a /etc/mdadm.conf file is a two step process.
You must first find the UUID of the array you wish to start, and then start the array with the UUID qualifier.

root@localhost / # mdadm --examine /dev/sdb2
/dev/sdb2:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : 5c718acf:61182c6e:0aced717:e4d9d364
           Name : rescue:1  (local to host rescue)
  Creation Time : Wed Apr 25 16:52:27 2012
     Raid Level : raid1
   Raid Devices : 2

 Avail Dev Size : 1048552 (512.07 MiB 536.86 MB)
     Array Size : 1048552 (512.07 MiB 536.86 MB)
    Data Offset : 24 sectors
   Super Offset : 8 sectors
          State : clean
    Device UUID : 299b2460:a79d36a8:b6992772:2379959b

    Update Time : Thu Jun 13 14:22:51 2013
       Checksum : af046248 - correct
         Events : 269


   Device Role : Active device 1
   Array State : .A ('A' == active, '.' == missing)
root@localhost / # 

Use the UUID to start the array

root@localhost / # mdadm --assemble /dev/md0 --run -u 5c718acf:61182c6e:0aced717:e4d9d364
mdadm: /dev/md0 has been started with 1 drive (out of 2).
root@localhost / # 

There is example of degrated array.

Add the array configuration information to /etc/mdadm.conf so you do not have to reference this KB again 😉

root@localhost / # mdadm --detail --scan >> /etc/mdadm.conf
root@localhost / #

Written by spectre

June 15th, 2013 at 8:09 pm

Posted in Arrays and Disks

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